Rigid conduit has been previously used as a riser coming from underground and extending above ground to a meter box on an exterior vertical wall of the building. Such rigid conduit riser is used for physical protection of service entrance cable and the like supplying electrical power to either a residential or a commercial building. Quite often, such rigid conduit has an L-shaped bend therein so that the lower end extends generally horizontally into a trench. The trench may extend perpendicular to the foundation or at any variation from 0.degree. to 180.degree.. The riser assembly will accommodate any trench angle extending from the foundation. The trench has previously been excavated so that an electrical cable could be laid therein, either direct burial cable or cable within a protective conduit which could connect to the lower end of the riser. Often, the earth in the trench would settle, and this would place undue strain on the direct burial cable, or the riser, and as a result the terminator fitting between the riser and the meter box could be broken loose. Thermal expansion and contraction with weather changes also caused high stress on such riser and terminator fitting. The riser assembly also accommodates varying meter heights as may be permitted by local codes, e.g., 4-ft. to 5-ft. meter heights are normally acceptable. The riser assembly will accommodate any height from 4 feet to 5 feet while providing adequate burial depth for the cable in the trench to conform with "cover" requirements of the National Electrical Code. In mobile home applications, the riser assembly accommodates settlement of the mobile home without driving the underground conduit up through the service panel.
The problem to be solved, therefore, is how to achieve a riser assembly which eliminates the stress on both the electrical cable and the fitting connection between the riser and the electrical box to which it is connected.
This problem is solved by an adjustable riser assembly comprising, in combination, a first rigid conduit having first and second ends, a bend of at least about 30 degrees in said first rigid conduit between said ends, a second rigid conduit having first and second ends, said first end of said second conduit having an enlarged diameter portion sufficient to receive the second end of said first conduit with a sliding fit, a fitting secured on said second end of said second conduit for connection to an electrical box on a substantially vertical wall of a building, said enlarged diameter portion on said first end of said second conduit being at least six inches long for telescoping adjustment with said second end of said first conduit, said telescoping adjustment establishing a close fitting sliding interconnection between said first and second conduits to accommodate ground settling and thermal expansion for a conduit or a direct underground burial cable leading to the building, and said first and second conduits and telescoping adjustment therebetween providing physical protection below and above ground for an electrical cable within said conduits.
Accordingly, an object of the invention is to provide an adjustable riser assembly which can automatically adjust in vertical height due to any settling of earth in the trench containing the cable or due to any thermal expansion or contraction.
Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing.